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      1 /* $NetBSD: ssdfb_spi.c,v 1.18 2025/09/13 14:10:44 thorpej Exp $ */
      2 
      3 /*
      4  * Copyright (c) 2019 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Tobias Nygren.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 __KERNEL_RCSID(0, "$NetBSD: ssdfb_spi.c,v 1.18 2025/09/13 14:10:44 thorpej Exp $");
     34 
     35 #include <sys/param.h>
     36 #include <sys/device.h>
     37 #include <sys/kernel.h>
     38 #include <dev/wscons/wsdisplayvar.h>
     39 #include <dev/rasops/rasops.h>
     40 #include <dev/spi/spivar.h>
     41 #include <dev/ic/ssdfbvar.h>
     42 #include "opt_fdt.h"
     43 #ifdef FDT
     44 #include <dev/fdt/fdtvar.h>
     45 #endif
     46 
     47 struct bs_state {
     48 	uint8_t	*base;
     49 	uint8_t	*cur;
     50 	uint8_t	mask;
     51 };
     52 
     53 struct ssdfb_spi_softc {
     54 	struct ssdfb_softc	sc;
     55 	spi_handle_t		sc_sh;
     56 #ifdef FDT
     57 	struct fdtbus_gpio_pin	*sc_gpio_dc;
     58 	struct fdtbus_gpio_pin	*sc_gpio_res;
     59 #endif
     60 	bool			sc_3wiremode;
     61 	bool			sc_late_dc_deassert;
     62 	uint8_t			sc_padding_cmd;
     63 };
     64 
     65 static int	ssdfb_spi_match(device_t, cfdata_t, void *);
     66 static void	ssdfb_spi_attach(device_t, device_t, void *);
     67 
     68 static int	ssdfb_spi_cmd_3wire(void *, uint8_t *, size_t, bool);
     69 static int	ssdfb_spi_xfer_rect_3wire_ssd1322(void *, uint8_t, uint8_t,
     70 		    uint8_t, uint8_t, uint8_t *, size_t, bool);
     71 
     72 static int	ssdfb_spi_cmd_4wire(void *, uint8_t *, size_t, bool);
     73 static int	ssdfb_spi_xfer_rect_4wire_sh1106(void *, uint8_t, uint8_t,
     74 		    uint8_t, uint8_t, uint8_t *, size_t, bool);
     75 static int	ssdfb_spi_xfer_rect_4wire_ssd1306(void *, uint8_t, uint8_t,
     76 		    uint8_t, uint8_t, uint8_t *, size_t, bool);
     77 static int	ssdfb_spi_xfer_rect_4wire_ssd1322(void *, uint8_t, uint8_t,
     78 		    uint8_t, uint8_t, uint8_t *, size_t, bool);
     79 static int	ssdfb_spi_xfer_rect_4wire_ssd1353(void *, uint8_t, uint8_t,
     80 		    uint8_t, uint8_t, uint8_t *, size_t, bool);
     81 
     82 static void	ssdfb_bitstream_init(struct bs_state *, uint8_t *);
     83 static void	ssdfb_bitstream_append(struct bs_state *, uint8_t, uint8_t);
     84 static void	ssdfb_bitstream_append_cmd(struct bs_state *, uint8_t);
     85 static void	ssdfb_bitstream_append_data(struct bs_state *, uint8_t *,
     86 		    size_t);
     87 static void	ssdfb_bitstream_final(struct bs_state *, uint8_t);
     88 
     89 CFATTACH_DECL_NEW(ssdfb_spi, sizeof(struct ssdfb_spi_softc),
     90     ssdfb_spi_match, ssdfb_spi_attach, NULL, NULL);
     91 
     92 static const struct device_compatible_entry compat_data[] = {
     93 	{ .compat = "solomon,ssd1306",	.value = SSDFB_PRODUCT_SSD1306_GENERIC },
     94 	{ .compat = "sino,sh1106",	.value = SSDFB_PRODUCT_SH1106_GENERIC },
     95 	{ .compat = "solomon,ssd1322",	.value = SSDFB_PRODUCT_SSD1322_GENERIC },
     96 	{ .compat = "solomon,ssd1353",	.value = SSDFB_PRODUCT_SSD1353_GENERIC },
     97 	{ .compat = "dep160128a",	.value = SSDFB_PRODUCT_DEP_160128A_RGB },
     98 	DEVICE_COMPAT_EOL
     99 };
    100 
    101 static int
    102 ssdfb_spi_match(device_t parent, cfdata_t match, void *aux)
    103 {
    104 	struct spi_attach_args *sa = aux;
    105 	int match_result;
    106 
    107 	if (spi_use_direct_match(sa, compat_data, &match_result)) {
    108 		return match_result;
    109 	}
    110 
    111 	return SPI_MATCH_DEFAULT;
    112 }
    113 
    114 static void
    115 ssdfb_spi_attach(device_t parent, device_t self, void *aux)
    116 {
    117 	struct ssdfb_spi_softc *sc = device_private(self);
    118 	struct cfdata *cf = device_cfdata(self);
    119 	struct spi_attach_args *sa = aux;
    120 	int flags = cf->cf_flags;
    121 	int error;
    122 
    123 	sc->sc.sc_dev = self;
    124 	sc->sc_sh = sa->sa_handle;
    125 	sc->sc.sc_cookie = (void *)sc;
    126 
    127 	if ((flags & SSDFB_ATTACH_FLAG_PRODUCT_MASK) == SSDFB_PRODUCT_UNKNOWN) {
    128 		const struct device_compatible_entry *dce =
    129 			spi_compatible_lookup(sa, compat_data);
    130 		if (dce)
    131 			flags |= (int)dce->value;
    132 		else
    133 			flags |= SSDFB_PRODUCT_SSD1322_GENERIC;
    134 	}
    135 
    136 	/*
    137 	 * SSD1306 and SSD1322 data sheets specify 100ns cycle time.
    138 	 */
    139 	error = spi_configure(self, sa->sa_handle, SPI_MODE_0,
    140 	    SPI_FREQ_MHz(10));
    141 	if (error) {
    142 		return;
    143 	}
    144 
    145 	/*
    146 	 * Note on interface modes.
    147 	 *
    148 	 * 3 wire mode sends 9 bit sequences over the MOSI, MSB contains
    149 	 * the bit that determines if the lower 8 bits are command or data.
    150 	 *
    151 	 * 4 wire mode sends 8 bit sequences and requires an auxiliary GPIO
    152 	 * pin for the command/data bit.
    153 	 */
    154 	devhandle_t devhandle = device_handle(self);
    155 	switch (devhandle_type(devhandle)) {
    156 #ifdef FDT
    157 	case DEVHANDLE_TYPE_OF: {
    158 		const int phandle = devhandle_to_of(devhandle);
    159 		sc->sc_gpio_dc =
    160 		    fdtbus_gpio_acquire(phandle, "dc-gpio", GPIO_PIN_OUTPUT);
    161 		if (!sc->sc_gpio_dc) {
    162 			sc->sc_gpio_dc = fdtbus_gpio_acquire(phandle,
    163 			    "cd-gpio", GPIO_PIN_OUTPUT);
    164 		}
    165 		sc->sc_3wiremode = (sc->sc_gpio_dc == NULL);
    166 		sc->sc_gpio_res =
    167 		    fdtbus_gpio_acquire(phandle, "res-gpio", GPIO_PIN_OUTPUT);
    168 		if (sc->sc_gpio_res) {
    169 			fdtbus_gpio_write_raw(sc->sc_gpio_res, 0);
    170 			DELAY(100);
    171 			fdtbus_gpio_write_raw(sc->sc_gpio_res, 1);
    172 			DELAY(100);
    173 		}
    174 		break;
    175 	    }
    176 #endif /* FDT */
    177 	default:
    178 		sc->sc_3wiremode = true;
    179 		break;
    180 	}
    181 
    182 	sc->sc.sc_cmd = sc->sc_3wiremode
    183 	    ? ssdfb_spi_cmd_3wire
    184 	    : ssdfb_spi_cmd_4wire;
    185 
    186 	switch (flags & SSDFB_ATTACH_FLAG_PRODUCT_MASK) {
    187 	case SSDFB_PRODUCT_SH1106_GENERIC:
    188 		sc->sc.sc_transfer_rect = sc->sc_3wiremode
    189 		    ? NULL
    190 		    : ssdfb_spi_xfer_rect_4wire_sh1106;
    191 		sc->sc_padding_cmd = SSDFB_CMD_NOP;
    192 		sc->sc_late_dc_deassert = true;
    193 		break;
    194 	case SSDFB_PRODUCT_SSD1306_GENERIC:
    195 		sc->sc.sc_transfer_rect = sc->sc_3wiremode
    196 		    ? NULL
    197 		    : ssdfb_spi_xfer_rect_4wire_ssd1306;
    198 		sc->sc_padding_cmd = SSDFB_CMD_NOP;
    199 		sc->sc_late_dc_deassert = true;
    200 		break;
    201 	case SSDFB_PRODUCT_SSD1322_GENERIC:
    202 		sc->sc.sc_transfer_rect = sc->sc_3wiremode
    203 		    ? ssdfb_spi_xfer_rect_3wire_ssd1322
    204 		    : ssdfb_spi_xfer_rect_4wire_ssd1322;
    205 		sc->sc_padding_cmd = SSD1322_CMD_WRITE_RAM;
    206 		break;
    207 	case SSDFB_PRODUCT_SSD1353_GENERIC:
    208 	case SSDFB_PRODUCT_DEP_160128A_RGB:
    209 		sc->sc.sc_transfer_rect = sc->sc_3wiremode
    210 		    ? NULL /* not supported here */
    211 		    : ssdfb_spi_xfer_rect_4wire_ssd1353;
    212 		break;
    213 	}
    214 
    215 	if (!sc->sc.sc_transfer_rect) {
    216 		aprint_error(": sc_transfer_rect not implemented\n");
    217 		return;
    218 	}
    219 
    220 	ssdfb_attach(&sc->sc, flags);
    221 
    222 	aprint_normal_dev(self, "%d-wire SPI interface\n",
    223 	    sc->sc_3wiremode == true ? 3 : 4);
    224 }
    225 
    226 static int
    227 ssdfb_spi_cmd_3wire(void *cookie, uint8_t *cmd, size_t len, bool usepoll)
    228 {
    229 	struct ssdfb_spi_softc *sc = (struct ssdfb_spi_softc *)cookie;
    230 	uint8_t bitstream[16 * 9 / 8];
    231 	struct bs_state s;
    232 
    233 	KASSERT(len > 0 && len <= 16);
    234 	ssdfb_bitstream_init(&s, bitstream);
    235 	ssdfb_bitstream_append_cmd(&s, *cmd);
    236 	cmd++;
    237 	len--;
    238 	ssdfb_bitstream_append_data(&s, cmd, len);
    239 	ssdfb_bitstream_final(&s, sc->sc_padding_cmd);
    240 
    241 	return spi_send(sc->sc_sh, s.cur - s.base, bitstream);
    242 }
    243 
    244 static int
    245 ssdfb_spi_xfer_rect_3wire_ssd1322(void *cookie, uint8_t fromcol, uint8_t tocol,
    246     uint8_t fromrow, uint8_t torow, uint8_t *p, size_t stride, bool usepoll)
    247 {
    248 	struct ssdfb_spi_softc *sc = (struct ssdfb_spi_softc *)cookie;
    249 	uint8_t bitstream[128 * 9 / 8];
    250 	struct bs_state s;
    251 	size_t rlen = (tocol + 1 - fromcol) * 2;
    252 	int error;
    253 
    254 	/*
    255 	 * Unlike iic(4), there is no way to force spi(4) to use polling.
    256 	 */
    257 	if (usepoll && !cold)
    258 		return 0;
    259 
    260 	ssdfb_bitstream_init(&s, bitstream);
    261 	ssdfb_bitstream_append_cmd(&s, SSD1322_CMD_SET_ROW_ADDRESS);
    262 	ssdfb_bitstream_append_data(&s, &fromrow, 1);
    263 	ssdfb_bitstream_append_data(&s, &torow, 1);
    264 	ssdfb_bitstream_append_cmd(&s, SSD1322_CMD_SET_COLUMN_ADDRESS);
    265 	ssdfb_bitstream_append_data(&s, &fromcol, 1);
    266 	ssdfb_bitstream_append_data(&s, &tocol, 1);
    267 	ssdfb_bitstream_append_cmd(&s, SSD1322_CMD_WRITE_RAM);
    268 	ssdfb_bitstream_final(&s, sc->sc_padding_cmd);
    269 	error = spi_send(sc->sc_sh, s.cur - s.base, bitstream);
    270 	if (error)
    271 		return error;
    272 
    273 	KASSERT(rlen <= 128);
    274 	while (fromrow <= torow) {
    275 		ssdfb_bitstream_init(&s, bitstream);
    276 		ssdfb_bitstream_append_data(&s, p, rlen);
    277 		ssdfb_bitstream_final(&s, sc->sc_padding_cmd);
    278 		error = spi_send(sc->sc_sh, s.cur - s.base, bitstream);
    279 		if (error)
    280 			return error;
    281 		fromrow++;
    282 		p += stride;
    283 	}
    284 
    285 	return 0;
    286 }
    287 
    288 static void
    289 ssdfb_bitstream_init(struct bs_state *s, uint8_t *dst)
    290 {
    291 	s->base = s->cur = dst;
    292 	s->mask = 0x80;
    293 }
    294 
    295 static void
    296 ssdfb_bitstream_append(struct bs_state *s, uint8_t b, uint8_t srcmask)
    297 {
    298 	while(srcmask) {
    299 		if (b & srcmask)
    300 			*s->cur |= s->mask;
    301 		else
    302 			*s->cur &= ~s->mask;
    303 		srcmask >>= 1;
    304 		s->mask >>= 1;
    305 		if (!s->mask) {
    306 			s->mask = 0x80;
    307 			s->cur++;
    308 		}
    309 	}
    310 }
    311 
    312 static void
    313 ssdfb_bitstream_append_cmd(struct bs_state *s, uint8_t cmd)
    314 {
    315 	ssdfb_bitstream_append(s, 0, 1);
    316 	ssdfb_bitstream_append(s, cmd, 0x80);
    317 }
    318 
    319 static void
    320 ssdfb_bitstream_append_data(struct bs_state *s, uint8_t *data, size_t len)
    321 {
    322 	while(len--) {
    323 		ssdfb_bitstream_append(s, 1, 1);
    324 		ssdfb_bitstream_append(s, *data++, 0x80);
    325 	}
    326 }
    327 
    328 static void
    329 ssdfb_bitstream_final(struct bs_state *s, uint8_t padding_cmd)
    330 {
    331 	while (s->mask != 0x80) {
    332 		ssdfb_bitstream_append_cmd(s, padding_cmd);
    333 	}
    334 }
    335 
    336 static void
    337 ssdfb_spi_4wire_set_dc(struct ssdfb_spi_softc *sc, int value)
    338 {
    339 #ifdef FDT
    340 	fdtbus_gpio_write_raw(sc->sc_gpio_dc, value);
    341 #else
    342 	panic("ssdfb_spi_4wire_set_dc");
    343 #endif
    344 }
    345 
    346 static int
    347 ssdfb_spi_cmd_4wire(void *cookie, uint8_t *cmd, size_t len, bool usepoll)
    348 {
    349 	struct ssdfb_spi_softc *sc = (struct ssdfb_spi_softc *)cookie;
    350 	int error;
    351 
    352 	ssdfb_spi_4wire_set_dc(sc, 0);
    353 	error = spi_send(sc->sc_sh, 1, cmd);
    354 	if (error)
    355 		return error;
    356 	if (len > 1) {
    357 		if (!sc->sc_late_dc_deassert)
    358 			ssdfb_spi_4wire_set_dc(sc, 1);
    359 		len--;
    360 		cmd++;
    361 		error = spi_send(sc->sc_sh, len, cmd);
    362 		if (error)
    363 			return error;
    364 	}
    365 
    366 	return 0;
    367 }
    368 
    369 static int
    370 ssdfb_spi_xfer_rect_4wire_sh1106(void *cookie, uint8_t fromcol, uint8_t tocol,
    371     uint8_t frompage, uint8_t topage, uint8_t *p, size_t stride, bool usepoll)
    372 {
    373 	struct ssdfb_spi_softc *sc = (struct ssdfb_spi_softc *)cookie;
    374 	size_t rlen = tocol + 1 - fromcol;
    375 	int error;
    376 	uint8_t cmd[] = {
    377 		SSDFB_CMD_SET_PAGE_START_ADDRESS_BASE + frompage,
    378 		SSDFB_CMD_SET_HIGHER_COLUMN_START_ADDRESS_BASE + (fromcol >> 4),
    379 		SSDFB_CMD_SET_LOWER_COLUMN_START_ADDRESS_BASE + (fromcol & 0xf)
    380 	};
    381 
    382 	if (usepoll && !cold)
    383 		return 0;
    384 
    385 	while (frompage <= topage) {
    386 		cmd[0] = SSDFB_CMD_SET_PAGE_START_ADDRESS_BASE + frompage;
    387 		ssdfb_spi_4wire_set_dc(sc, 0);
    388 		error = spi_send(sc->sc_sh, sizeof(cmd), cmd);
    389 		if (error)
    390 			return error;
    391 		ssdfb_spi_4wire_set_dc(sc, 1);
    392 		error = spi_send(sc->sc_sh, rlen, p);
    393 		if (error)
    394 			return error;
    395 		frompage++;
    396 		p += stride;
    397 	}
    398 
    399 	return 0;
    400 }
    401 
    402 static int
    403 ssdfb_spi_xfer_rect_4wire_ssd1306(void *cookie, uint8_t fromcol, uint8_t tocol,
    404     uint8_t frompage, uint8_t topage, uint8_t *p, size_t stride, bool usepoll)
    405 {
    406 	struct ssdfb_spi_softc *sc = (struct ssdfb_spi_softc *)cookie;
    407 	size_t rlen = tocol + 1 - fromcol;
    408 	int error;
    409 	uint8_t cmd[] = {
    410 		SSD1306_CMD_SET_MEMORY_ADDRESSING_MODE,
    411 		SSD1306_MEMORY_ADDRESSING_MODE_HORIZONTAL,
    412 		SSD1306_CMD_SET_COLUMN_ADDRESS,
    413 		fromcol,
    414 		tocol,
    415 		SSD1306_CMD_SET_PAGE_ADDRESS,
    416 		frompage,
    417 		topage
    418 	};
    419 
    420 	if (usepoll && !cold)
    421 		return 0;
    422 
    423 	ssdfb_spi_4wire_set_dc(sc, 0);
    424 	error = spi_send(sc->sc_sh, sizeof(cmd), cmd);
    425 	if (error)
    426 		return error;
    427 	ssdfb_spi_4wire_set_dc(sc, 1);
    428 
    429 	while (frompage <= topage) {
    430 		error = spi_send(sc->sc_sh, rlen, p);
    431 		if (error)
    432 			return error;
    433 		frompage++;
    434 		p += stride;
    435 	}
    436 
    437 	return 0;
    438 }
    439 
    440 static int
    441 ssdfb_spi_xfer_rect_4wire_ssd1322(void *cookie, uint8_t fromcol, uint8_t tocol,
    442     uint8_t fromrow, uint8_t torow, uint8_t *p, size_t stride, bool usepoll)
    443 {
    444 	struct ssdfb_spi_softc *sc = (struct ssdfb_spi_softc *)cookie;
    445 	size_t rlen = (tocol + 1 - fromcol) * 2;
    446 	int error;
    447 	uint8_t cmd;
    448 	uint8_t data[2];
    449 
    450 	if (usepoll && !cold)
    451 		return 0;
    452 
    453 	ssdfb_spi_4wire_set_dc(sc, 0);
    454 	cmd = SSD1322_CMD_SET_ROW_ADDRESS;
    455 	error = spi_send(sc->sc_sh, sizeof(cmd), &cmd);
    456 	if (error)
    457 		return error;
    458 	ssdfb_spi_4wire_set_dc(sc, 1);
    459 	data[0] = fromrow;
    460 	data[1] = torow;
    461 	error = spi_send(sc->sc_sh, sizeof(data), data);
    462 	if (error)
    463 		return error;
    464 
    465 	ssdfb_spi_4wire_set_dc(sc, 0);
    466 	cmd = SSD1322_CMD_SET_COLUMN_ADDRESS;
    467 	error = spi_send(sc->sc_sh, sizeof(cmd), &cmd);
    468 	if (error)
    469 		return error;
    470 	ssdfb_spi_4wire_set_dc(sc, 1);
    471 	data[0] = fromcol;
    472 	data[1] = tocol;
    473 	error = spi_send(sc->sc_sh, sizeof(data), data);
    474 	if (error)
    475 		return error;
    476 
    477 	ssdfb_spi_4wire_set_dc(sc, 0);
    478 	cmd = SSD1322_CMD_WRITE_RAM;
    479 	error = spi_send(sc->sc_sh, sizeof(cmd), &cmd);
    480 	if (error)
    481 		return error;
    482 
    483 	ssdfb_spi_4wire_set_dc(sc, 1);
    484 	while (fromrow <= torow) {
    485 		error = spi_send(sc->sc_sh, rlen, p);
    486 		if (error)
    487 			return error;
    488 		fromrow++;
    489 		p += stride;
    490 	}
    491 
    492 	return 0;
    493 }
    494 
    495 static int
    496 ssdfb_spi_xfer_rect_4wire_ssd1353(void *cookie, uint8_t fromcol, uint8_t tocol,
    497     uint8_t fromrow, uint8_t torow, uint8_t *p, size_t stride, bool usepoll)
    498 {
    499 	struct ssdfb_spi_softc *sc = (struct ssdfb_spi_softc *)cookie;
    500 	size_t rlen = (tocol + 1 - fromcol) * 3;
    501 	uint8_t bitstream[160 * 3];
    502 	uint8_t *dstp, *srcp, *endp;
    503 	int error;
    504 	uint8_t cmd;
    505 	uint8_t data[2];
    506 
    507 	if (usepoll && !cold)
    508 		return 0;
    509 
    510 	ssdfb_spi_4wire_set_dc(sc, 0);
    511 	cmd = SSD1353_CMD_SET_ROW_ADDRESS;
    512 	error = spi_send(sc->sc_sh, sizeof(cmd), &cmd);
    513 	if (error)
    514 		return error;
    515 	ssdfb_spi_4wire_set_dc(sc, 1);
    516 	data[0] = fromrow;
    517 	data[1] = torow;
    518 	if (sc->sc.sc_upsidedown) {
    519 		/* fix picture outside frame on 160x128 panel */
    520 		data[0] += 132 - sc->sc.sc_p->p_height;
    521 		data[1] += 132 - sc->sc.sc_p->p_height;
    522 	}
    523 	error = spi_send(sc->sc_sh, sizeof(data), data);
    524 	if (error)
    525 		return error;
    526 
    527 	ssdfb_spi_4wire_set_dc(sc, 0);
    528 	cmd = SSD1353_CMD_SET_COLUMN_ADDRESS;
    529 	error = spi_send(sc->sc_sh, sizeof(cmd), &cmd);
    530 	if (error)
    531 		return error;
    532 	ssdfb_spi_4wire_set_dc(sc, 1);
    533 	data[0] = fromcol;
    534 	data[1] = tocol;
    535 	error = spi_send(sc->sc_sh, sizeof(data), data);
    536 	if (error)
    537 		return error;
    538 
    539 	ssdfb_spi_4wire_set_dc(sc, 0);
    540 	cmd = SSD1353_CMD_WRITE_RAM;
    541 	error = spi_send(sc->sc_sh, sizeof(cmd), &cmd);
    542 	if (error)
    543 		return error;
    544 
    545 	ssdfb_spi_4wire_set_dc(sc, 1);
    546 	KASSERT(rlen <= sizeof(bitstream));
    547 	while (fromrow <= torow) {
    548 		/* downconvert each row from 32bpp rgba to 18bpp panel format */
    549 		dstp = bitstream;
    550 		endp = dstp + rlen;
    551 		srcp = p;
    552 		while (dstp < endp) {
    553 			*dstp++ = (*srcp++) >> 2;
    554 			*dstp++ = (*srcp++) >> 2;
    555 			*dstp++ = (*srcp++) >> 2;
    556 			srcp++;
    557 		}
    558 		error = spi_send(sc->sc_sh, rlen, bitstream);
    559 		if (error)
    560 			return error;
    561 		fromrow++;
    562 		p += stride;
    563 	}
    564 
    565 	return 0;
    566 }
    567